An optical fiber long length side-grinding device with controllable and high precision grinding thickness,and a setup for high-precision polishing of the optical fiber section by using an arc discharge method are self-made. The grinding precision is 0.01 μm,the grinding length can be longer than 100 mm,and multi-fibers can be grinded at the same time. By using the devices,the side grinding thickness of the polarization-maintaining fiber Bragg grating (PMF-FBG) can be controlled,and long length,high precision controllable PMF-FBG can be fabricated. The span of the two wavelengths of the PMF-FBG can be controlled accurately. The experiment results show that when the radius of the grinding side of the PMF-FBG changed from 125 μm to 65 μm,the wavelength span of the PMF-FBG changed from 0.34 nm to 0.208 nm.